Communications methods and apparatus using physical attachment point identifiers which support dual communications links

ABSTRACT

Methods and apparatus for routing messages between an end node and an access node via another access node are described. Physical layer identification information is used when identifying a remote, e.g., adjacent, access node as a message destination. Thus, when a connection identifier based on one or more physical layer identifiers is available to a wireless terminal, e.g., from one or more downlink signals received from a destination access node, the wireless terminal can use the connection identifier corresponding to the destination node to route a message via an access node with which it has an established uplink connection. Such connection identifier information can be used even when other addressing information, e.g., network layer address information, associated with the destination access node, may not be available to the wireless terminal.

FIELD OF THE INVENTION

This invention relates to communications system and, more particularly,to methods and apparatus for routing messages based on physical layerinformation in wireless, e.g., cellular, communications networks.

BACKGROUND OF INVENTION

The Open System Interconnection (OSI) reference model is useful inexplaining various communications and routing operations. The OSIreference model includes 7 layers with the application layer being thetop most layer and the Physical Layer being the lowest layer. Thephysical layer is the layer which deals with actual physical connectionsand attributes of the physical connections in the system. Above thephysical layer is a Data Link layer, sometimes referred to as the linklayer. The link layer (Layer 2 in the OSI model) is sometimes describedas a technology specific transfer layer. Above the link layer is thenetwork layer (OSI Layer 3) where network routing and relaying issupported. The network layer is sometimes referred to as the packetlayer. It is at the network layer that routing of messages/packetsthrough the network is performed, e.g., on one or more paths. Differentaddressing may be used for directing messages and signals at thedifferent levels. For example, a network address such as an IP address,maybe used for routing messages/packets at the network layer level. MACaddresses maybe use for controlling routing of messages at the data linklayer level. At the lowest level of the OSI model, the physical level,one or more physical identifiers have a relationship to an actualphysical attribute or characteristic of a source or destination device.An understanding of the different communication layers and differentaddressing techniques used for each of the layers will facilitate anunderstanding of the present invention.

Communications systems frequently include a plurality of network nodeswhich are coupled to access nodes through which end nodes, e.g., mobiledevices, are coupled to the network. Network nodes may be arranged in ahierarchy. End nodes typically communicate with access nodes directlythrough connections that have been established with said access nodes.Such systems usually rely on the existence of a bidirectionalcommunications link between an access node and end not to support twoway communications between an end node and an access node. Note that insuch systems the end node normally does not know the network layeraddress of a target destination access node but may be cognizant ofinformation that it can receive over broadcast channels which typicallycan include physical layer identifier that are normally not used in suchsystems for message routing. This approach results in handoff delays andpacket loss when the end node is only able to maintain one singlebidirectional communications link at the time.

It should then be appreciated that there is a need for methods andapparatus that allows an end node that has no current uplinkcommunications link to a target access node to communicate with saidtarget access node via another access node with which the end node has acurrent uplink communications link even when said end node does nto knowthe network address of the target access node.

In some systems end nodes are capable of maintaining multiplebidirectional communications links with different access nodes at thesame time. However, such systems typically require the end nodes to sendmessages intended for a specific access node, with which an end node hasa connection, over the link that is directly connected to that specificaccess node. This approach, in some cases, is inefficient since links,especially when they are wireless links, tend to fluctuate in terms ofquality (e.g., delay and loss characteristics). As a result the link tothe target destination access node may not be the best link available tothe end node at the time a message to said target destination accessnode needs to be sent. Typically this limitation is overcome byresorting to network layer communications that can be routed viamultiple hops due to the use of network layer addresses (e.g., IPaddresses). This approach of using network layer addresses is alsoinefficient especially when the messaging has to do with link layerspecific functions, since network layer messages tend to be much largerthan link layer messages in some systems. Such inefficient signaling isnot well suited for communications over resource restricted air links.

It should then be appreciated that there is also a need for a methodthat allows an end node to send messages over any of its availablewireless communications links independently of the access node themessage is intended. It would be desirable is such messages could besent, at least in some embodiments, without having to resort toinefficient network layer communications, e.g., communications involvingthe use of network layer addresses, such as IP layer addresses, forrouting information to the destination access node.

SUMMARY OF THE INVENTION

The present invention is directed to methods and apparatus for routingmessages between an end node and an access node via another access node.The methods and apparatus of the invention support the use of physicallayer identification information when identifying a remote, e.g.,adjacent, access node as a message destination. Thus, when a connectionidentifier based on one or more physical layer identifiers is availableto a wireless terminal, e.g., from one or more downlink signals receivedfrom a destination access node, the wireless terminal can use theconnection identifier corresponding to the destination node to route amessage via an access node with which it has an established uplinkconnection. Such connection identifier information can be used even whenother addressing information, e.g., network layer address information,associated with the destination access node, may not be available to thewireless terminal.

Various novel features are directed to end node methods of receivingbroadcast information from an access node and determining a physicalattachment point identifier, for example a connection identifiercorresponding to the access node. Other features are directed to thesending of signals to one access node including a connection identifiercorresponding to another access node. The connection identifier is basedon one or more pieces of information which provide information relatingto a physical layer attachment point. Thus, in accordance with theinvention physical layer information can be used as a connectionidentifier.

In accordance with the invention, access nodes store information mappingconnection identifiers which are based on physical layer identificationinformation to one or more higher level addresses. The mappinginformation is stored in the access nodes. Access nodes include mappinginformation for connections identifiers corresponding to physical layerattachment points which are local to the access node in addition toconnection identifiers corresponding to physical layer attachment pointsof other, e.g., neighboring, access nodes. This allows routing betweenphysically adjacent base stations to be performed based on physicallayer connection identifiers without the need for a wireless terminal totransmit a link layer or network layer address over the air when sendinga message which is to be delivered to a neighboring access node via anexisting connection with an access node currently serving the wirelessterminal.

Thus various features of the invention are directed to end node methodsof receiving signals from access nodes indicating an identifier toaccess node address resolution failure and causing said end node to sendneighbor notification messages for the establishment of new access nodeneighbors.

While some features are directed to wireless terminal methods andapparatus, as well as to novel messages of the invention stored in awireless terminal, other features are directed to novel access nodemethods and apparatus. The invention is also directed to data storagedevices, e.g., memory devices, which store one or more of the novelmessages of the present invention.

While various embodiments have been discussed in the summary above, itshould be appreciated that not necessarily all embodiments include thesame features and some of the features described above are not necessarybut can be desirable in some embodiments. Numerous additional features,embodiments and benefits of the present invention are discussed in thedetailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a network diagram of an exemplary communicationssystem implemented in accordance with the present invention.

FIG. 2 illustrates an exemplary end node implemented in accordance withthe present invention.

FIG. 3 illustrates an exemplary access node implemented in accordancewith the present invention.

FIG. 4 illustrates an exemplary Connection Identifier implementedaccording to this invention.

FIG. 5 illustrates an exemplary message using the Connection Identifierof FIG. 4 implemented according to this invention.

FIG. 6 illustrates exemplary signaling performed in accordance with thepresent invention when an end node maintains a bidirectional connectionto one access node and wants to communicate with another access node.

FIG. 7 illustrates exemplary signaling performed in accordance with thepresent invention when an end node maintains bidirectional connectionswith multiple access nodes.

FIG. 8 illustrates exemplary signaling performed in accordance with thepresent invention when an end node triggers a neighbor discovery processbetween two access nodes.

FIG. 9 illustrates an exemplary PID to higher level address resolutiontable which may be used for mapping between (to/from) PIDs andcorresponding higher level addresses.

DETAILED DESCRIPTION

The methods and apparatus of the present invention for routing messagesbased on physical layer information, e.g., physical layer indentifiers,which can be used to support communications sessions with one or moreend nodes, e.g., mobile devices. The method and apparatus of theinvention can be used with a wide range of communications systems. Forexample the invention can be used with systems which support mobilecommunications devices such as notebook computers equipped with modems,PDAs, and a wide variety of other devices which support wirelessinterfaces in the interests of device mobility.

FIG. 1 illustrates an exemplary communication system 100 implemented inaccordance with the present invention, e.g., a cellular communicationnetwork, which comprises a plurality of nodes interconnected bycommunications links. Exemplary communications system 100 is, e.g., amultiple access spread spectrum orthogonal frequency divisionmultiplexing (OFDM) wireless communications system. Nodes in theexemplary communication system 100 exchange information using signals,e.g., messages, based on communication protocols, e.g., the InternetProtocol (IP). The communications links of the system 100 may beimplemented, for example, using wires, fiber optic cables, and/orwireless communications techniques. The exemplary communication system100 includes a plurality of end nodes 144, 146, 144′, 146′, 144″, 146″,which access the communication system via a plurality of access nodes140, 140′, 140″. The end nodes 144, 146, 144′, 146′, 144″, 146″ may be,e.g., wireless communication devices or terminals, and the access nodes140, 140′, 140″ may be, e.g., base stations. The base stations may beimplemented as wireless access routers. The exemplary communicationsystem 100 also includes a number of other nodes 104, 106, 110, and 112,used to provide interconnectivity or to provide specific services orfunctions. Specifically, the exemplary communication system 100 includesa Server 104, used to support transfer and storage of state pertainingto end nodes. The Server node 104 may be, for example, an AAA server, orit may be a Context Transfer Server, or it may be a server includingboth AAA server functionality and Context Transfer server functionality.

The FIG. 1 exemplary system 100 depicts a network 102 that includes theServer 104 and the node 106, which are connected to an intermediatenetwork node 110 by a corresponding network link 105 and 107,respectively. The intermediate network node 110 in the network 102 alsoprovides interconnectivity to network nodes that are external from theperspective of the network 102 via network link 111. Network link 111 isconnected to another intermediate network node 112, which providesfurther connectivity to a plurality of access nodes 140, 140′, 140″ vianetwork links 141, 141′, 141″, respectively.

Each access node 140, 140′, 140″ is depicted as providing connectivityto a plurality of N end nodes (144, 146), (144′, 146′), (144″, 146″),respectively, via corresponding access links (145, 147), (145′, 147′),(145″, 147″), respectively. In the exemplary communication system 100,each access node 140, 140′, 140″ is depicted as using wirelesstechnology, e.g., wireless access links, to provide access. A radiocoverage area, e.g., communications cell, 148, 148′, 148″ of each accessnode 140, 140′, 140″, respectively, is illustrated as a circlesurrounding the corresponding access node.

The exemplary communication system 100 is subsequently used as a basisfor the description of various embodiments of the invention. Alternativeembodiments of the invention include various network topologies, wherethe number and type of network nodes, the number and type of accessnodes, the number and type of end nodes, the number and type of Serversand other Agents, the number and type of links, and theinterconnectivity between nodes may differ from that of the exemplarycommunication system 100 depicted in FIG. 1.

In various embodiments of the present invention some of the functionalentities depicted in FIG. 1 may be omitted or combined. The location orplacement of these functional entities in the network may also bevaried.

FIG. 2 provides a detailed illustration of an exemplary end node 200,e.g., wireless terminal such as a mobile node, implemented in accordancewith the present invention. The exemplary end node 200, depicted in FIG.2, is a detailed representation of an apparatus that may be used as anyone of the end nodes 144, 146, 144′, 146′, 144″, 146″, depicted inFIG. 1. In the FIG. 2 embodiment, the end node 200 includes a processor204, a wireless communication interface 230, a user input/outputinterface 240 and memory 210 coupled together by bus 206. Accordingly,via bus 206 the various components of the end node 200 can exchangeinformation, signals and data. The components 204, 206, 210, 230, 240 ofthe end node 200 are located inside a housing 202.

The wireless communication interface 230 provides a mechanism by whichthe internal components of the end node 200 can send and receive signalsto/from external devices and network nodes, e.g., access nodes. Thewireless communication interface 230 includes, e.g., a receiver module232 with a corresponding receiving antenna 236 and a transmitter module234 with a corresponding transmitting antenna 238 used for coupling theend node 200 to other network nodes, e.g., via wireless communicationschannels. In some embodiments, the transmitter module 234 includes anorthogonal frequency division multiplexing (OFDM) transmitter.

The exemplary end node 200 also includes a user input device 242, e.g.,keypad, and a user output device 244, e.g., display, which are coupledto bus 206 via the user input/output interface 240. Thus, userinput/output devices 242, 244 can exchange information, signals and datawith other components of the end node 200 via user input/outputinterface 240 and bus 206. The user input/output interface 240 andassociated devices 242, 244 provide a mechanism by which a user canoperate the end node 200 to accomplish various tasks. In particular, theuser input device 242 and user output device 244 provide thefunctionality that allows a user to control the end node 200 andapplications, e.g., modules, programs, routines and/or functions, thatexecute in the memory 210 of the end node 200.

The processor 204 under control of various modules, e.g., routines,included in memory 210 controls operation of the end node 200 to performvarious signaling and processing as discussed below. The modulesincluded in memory 210 are executed on startup or as called by othermodules. Modules may exchange data, information, and signals whenexecuted. Modules may also share data and information when executed. Inthe FIG. 2 embodiment, the memory 210 of end node 200 of the presentinvention includes a signaling/control module 212 and signaling/controldata 214.

The signaling/control module 212 controls processing relating toreceiving and sending signals, e.g., messages, for management of stateinformation storage, retrieval, and processing. Signaling/control data214 includes state information, e.g., parameters, status and/or otherinformation relating to operation of the end node. In particular, thesignaling/control data 214 includes configuration information 216, e.g.,end node identification information, and operational information 218,e.g., information about current processing state, status of pendingresponses, etc. The module 212 accesses and/or modify the data 214,e.g., updating the configuration information 216 and/or the operationalinformation 218.

The message generation module 251 is responsible for generating messagesfor various operations of the end node 200. Neighbor notificationmessage 280 and signaling message 281 are exemplary messages generatedaccording to this invention.

The link selection module 213 is responsible for selecting a link, e.g.,the best link, from the plurality of links available to end node 200 forthe transmission of the next message ready to be transmitted by end node200. The link selection algorithm is based on various link qualityparameters including at least some of but not limited to link latency,link channel conditions, link error rate, and link transmission powerrequirements.

The physical layer attachment point identifier (PID) determinationmodule 270 is responsible for determining the PID corresponding tobroadcast signals received from an access node. The PID determinationmodule 270 includes a cell identification module 271, a carrieridentification module 272, and a sector identification module 273. Insome but not all embodiments, a combination of a cell identifier,carrier identifier and sector identifier are used as physical attachmentpoint identifiers. Each of these identifier elements corresponds tophysical layer identification information. For example, the cellidentifier identifies a physical cell or cell type. The carrieridentifier identifies the physical carrier, e.g., the carrier frequencyor tone block while the sector identifier identifies a sector in acorresponding cell. Not all of this information need be used toimplement a PID and the particular element of a PID may vary dependingon the system implementation. For example, in a system which does notuse sectorized cells there would be no need for a sector ID. Similarly,in a single carrier system there may be no need for a carrier ID. Makinga PID determination, in one exemplary system, includes the steps ofoperating the cell identification module 271 for the determination of acell identifier, operating the carrier identification module 272 for thedetermination of a carrier identifier and operating the sectoridentification module 273 for the determination of a sector identifier.Thus, it should be appreciated that different signals which pass througha single physical transmitter element, e.g., antenna, can correspond todifferent physical layer attachment points, e.g., where each of thedifferent physical layer attachment points may be uniquely identified atleast within a local area, by a combination of physical identifiers. Forexample, it should be appreciated that a combination of an antenna orsector identifier in combination with a first carrier identifier mightbe used to identify a first physical layer attachment point while asecond carrier identifier in combination with the same antenna or sectoridentifier may be used to identify a second physical layer attachmentpoint.

The physical layer attachment point identifiers (PIDs) information 260is a list of PIDs, (PID1 261, PID2 262) which are PIDs determined usingthe PID determination module 260. One exemplary implementation of aphysical layer attachment point identifiers (PIDs) may be a connectionidentifier (CID) which may be included in messages when sending and/orreceiving messages. Particular exemplary CIDs are discussed furtherbelow.

Memory 210 also includes a neighbor notification module 290, a messagetransmission control module 292, and a link establishment module 294.The neighbor notification module 290 is used for transmitting a neighbornotification, e.g., a neighbor notification message 280, to accessnodes. Message transmission control module 292 is used for controllingthe transmitter module 234. Link establishment module 294 is used forestablishing a wireless communications links with access nodes.

FIG. 3 provides a detailed illustration of an exemplary access node 300implemented in accordance with the present invention. The exemplaryaccess node 300, depicted in FIG. 3, is a detailed representation of anapparatus that may be used as any one of the access nodes 140, 140′,140″ depicted in FIG. 1. In the FIG. 3 embodiment, the access node 300includes a processor 304, memory 310, a network/internetwork interface320 and a wireless communication interface 330, coupled together by bus306. Accordingly, via bus 306 the various components of the access node300 can exchange information, signals and data. The components 304, 306,310, 320, 330 of the access node 300 are located inside a housing 302.

The network/internetwork interface 320 provides a mechanism by which theinternal components of the access node 300 can send and receive signalsto/from external devices and network nodes. The network/internetworkinterface 320 includes, a receiver module 322 and a transmitter module324 used for coupling the node 300 to other network nodes, e.g., viacopper wires or fiber optic lines. The wireless communication interface330 also provides a mechanism by which the internal components of theaccess node 300 can send and receive signals to/from external devicesand network nodes, e.g., end nodes. The wireless communication interface330 includes, e.g., a receiver module 332 with a corresponding receivingantenna 336 and a transmitter module 334 with a correspondingtransmitting antenna 338. The interface 330 is used for coupling theaccess node 300 to other network nodes, e.g., via wireless communicationchannels.

The processor 304 under control of various modules, e.g., routines,included in memory 310 controls operation of the access node 300 toperform various signaling and processing. The modules included in memory310 are executed on startup or as called by other modules that may bepresent in memory 310. Modules may exchange data, information, andsignals when executed. Modules may also share data and information whenexecuted.

In the FIG. 3 embodiment, the memory 310 of the access node 300 of thepresent invention includes a signal generation module 314 for thegeneration of signals, a packet routing module 350 responsible for therouting of signals and messages, a mapping module 312 that isresponsible for mapping PIDs to network layer addresses, an addressresolution table 311 including PID to IP address mappings 317. Memory310 also includes an end node identification module 351 identifying endnodes with which the access node 300 is in communications with, uplinkresource allocation information 340 responsible for allocating uplinkresources to end nodes, including resources allocated to an end node X341 and, downlink resource allocation information 345 responsible forallocating downlink resources to end nodes, including resourcesallocated to an end node X 346.

Referring now briefly to FIG. 9, FIG. 9 illustrates an addressresolution table 311′ which may be used as the address resolution table311 shown in FIG. 3. The address resolution table 311′ includes PIDs902, 904, 906, 908, 910, 912 and information indicating thecorresponding IP addresses 903, 905, 907, 909, 911 and 913,respectively. The PIDs are each unique locally, e.g., the PIDs ofimmediately adjacent cells are unique from one another. Note that thecontent of the PIDs may vary depending on the physical characteristicsof the access node and number of physical layer attachment pointssupported by the access node to which the PID corresponds. In the FIG. 9example, PIDs 902, 904 correspond to a first access node (AN 1) whichsupports two sectors which use the same carrier. Accordingly, in thecase of AN 1, it is sufficient for the PID to include a cell identifierand a sector type identifier to uniquely identify the physical layerattachment points in the cell. PIDs 906, 908, 910 correspond to a cellwhich supports multiple carriers and multiple sectors. Accordingly, thePIDs for access node 2 are implemented as CIDs in the same manner asused in various exemplary embodiments discussed further herein. PID 912corresponds to a third access node which includes a single sector anduses a single carrier. Accordingly, it is sufficient for PID 6 whichcorresponds to the third access node to include just a cell identifieralthough additional physical layer identification, e.g., a sector and/orcarrier identifier. The inclusion of such additional information may bedesirable where, from a processing perspective, consistent PID formatsacross multiple cells is desirable.

Referring now to FIG. 4, FIG. 4 illustrates an exemplary ConnectionIDentifier (CID) 400 implemented according to this invention. CID 400includes a Slope 410, which is a cell Identifier, a Sector 420 which isa Sector Identifier and a Carrier 430, which is a carrier frequencyidentifier also known as tone block identifier.

In an exemplary communication system using OFDM technology, in thephysical layer, the spectrum is divided into a number of tones andreused in cells and sectors in neighboring geographical areas. In orderto improve the interference characteristics, the tones used in eachcell/sector hop over time, and different cells and sectors inneighboring geographical areas use different hopping sequences, whichspecify how the tones shall hop. The hopping sequences are generatedusing a predetermined function controlled with two input variables,namely, the cell identifier, e.g., slope value, and a sector identifier.The sector identifier may be implemented as a sector type identifierthat indicates which of a plurality of possible sector types aparticular sector corresponds to. In one embodiment, the slope value isan integer from 1 to 112, and the sector identifier value is an integerfrom 0 to 5. Neighboring cells and sectors use different pairs of slopeand sector identifier so that the generated hopping sequences aredifferent. In one embodiment, all the sectors in a cell use the sameslope value but different sector identifiers, and neighboring, e.g.,physically adjacent, cells use different slope values.

Furthermore, the exemplary OFDM communication system, in someembodiments, uses multiple carriers or tone blocks, so that theavailable tones are grouped into multiple tone blocks. Tones in a toneblock are preferably contiguous. In one exemplary system, hopping of thetones in a given tone block is limited to that tone block. That is, thehopping sequences are such that the tones can hop within the tone blockbut cannot hop across multiple tone blocks. Tone blocks are indexed witha carrier identifier. In one embodiment, the carrier identifier is aninteger 0, 1, or 2.

When an end node sets up a connection to get wireless networkingservices, the entity on the network side is an access node, e.g., a basestation in a cell/sector, and the connection is defined with respect toa single tone block. Therefore, in the above exemplary OFDMcommunication system, a combination of slope, sector identifier andcarrier identifier can be used as a locally unique identifier thatidentifies the connection for the wireless terminal. The combination isthus a connection identifier based on one or more physical layeridentifiers. In one embodiment, multiple wireless terminals can haveconnections with the same base station cell/sector on the same toneblock. Those connections normally will share the same connectionidentifier since they are connected to the same physical layerattachment point as defined by the combination of cell, sector and toneblock. The combination of the connection identifier and a wirelessterminal identifier can be used to indicate a communication connectionwith a particular wireless terminal.

In general, the connection identifier is a number or a combination ofnumbers that locally uniquely identifies a connection. In variousembodiments, the number or numbers are physical layer characteristicparameters. In another embodiment, e.g., an exemplary embodiment of aCDMA communication system, the connection identifier can be thecombination of a pseudo noise (PN) sequence offset and anotherparameter, e.g., a carrier identifier if multiple carriers are used.

FIG. 5 illustrates an exemplary message 500, in accordance with thepresent invention, which uses the Connection Identifier of FIG. 4.Exemplary message 500 is a link layer message which includes a CIDdestination/source address. The CID destination/source address is anoptional field in link layer messages in accordance with someembodiments of the present invention. Link layer message 500 includes aLink Layer Control (LLC) Type field 510 identifying the type of MessageBody 530 included in the message 500. CID 520 is a Connection ID in theform of the Connection ID 400 of FIG. 4. In one embodiment of thisinvention the CID field 520 identifies a destination physical attachmentpoint when sent from an end node to an access node in accordance withthe invention and identifies a source physical attachment when sent froman access node to an end node in accordance with the invention.

FIG. 6 illustrates an exemplary communications method and correspondingsignaling performed in accordance with various exemplary embodiments ofthe invention. In FIG. 6 end node 630 communicates with access node 620via access node 610 without a wireless uplink link between end node 630and access node 620 and without the end node having to know an IPaddress of the access node 620. The signaling is illustrated in thecontext of exemplary system 100 illustrated in FIG. 1. Access Nodes 610and 620 are similar to access nodes 140, 140′ and 140″ of system 100 inFIG. 1 and they are implemented according to the access node 300 of FIG.3. The End Node 630 is similar to end node 144, 146, 144′, 146′, 144″and 146″ of system 100 in FIG. 1, and it is implemented according to endnode 200 in FIG. 2.

In FIG. 6, end node 630 maintains a bidirectional link with access node610, which means that it can send messages to and receive message fromaccess node 610. End node 630 in FIG. 6, although inside thetransmission range of access node 620, does not have an uplink withaccess node 620. This means that while end node 630 can receive andprocess broadcast information sent by access node 620 (e.g., broadcastmessages 640), end node 630 can not send messages to access node 620over the air and access node 620 can not receive and process messagessent to it by end node 630 over the air interface. In one embodiment ofthis invention this may be because end node 630 and access node 620 donot have sufficient timing synchronization. Due to certain limitations,e.g., limited hardware capability, end node 630 may not be able toestablish an uplink connection with access node 620 while end node 630currently has a bidirectional connection with access node 610. In oneembodiment, the uplinks used by access node 610 and access node 620 arein different carriers, e.g., the frequency band of the uplink used byaccess node 610 is different from the frequency band of the uplink usedby access node 620. If end node 630 can only generate uplink signal inone band at a given time, for example, because end node 630 only has oneradio frequency (RF) chain due to cost considerations, then end node 630cannot simultaneously maintain two uplink connections in two separatefrequency bands. In another embodiment where the uplinks used by accessnodes 610 and 620 are in the same band, the two uplinks may not be timesynchronized, because the two access nodes are not time synchronized orbecause of the difference in the propagation delay for the signal toreach access nodes 610 and 620 from the end node 630. If end node 630can generate just one uplink signal according to one timingsynchronization scheme at a time, for example, because end node 630 hasa single digital processing chain limited to one timing scheme at atime, then end node 630 cannot simultaneously maintain two uplinkconnections, when the connections are not sufficiently timingsynchronized with one another.

End node 630 receives broadcast signal(s) 640 which are transmitted byaccess node 620. The signal(s) 640, according to the embodiment of thisinvention, are sufficient to determine the Connection ID, similar to CID400 of FIG. 4, corresponding to the specific physical attachment ofaccess node 620 that transmits broadcast signal 640. The signals orsignals 640 may include beacon and/or pilot signals which may betransmitted over one or more symbol transmission time periods.

End node 630 transmits a message 650 to access node 610. In an exemplaryembodiment of this invention, said message 650 is the same as, orsimilar to, exemplary message 500 of FIG. 5. The CID field, equivalentto CID 520 of FIG. 5, of said message 650 is set to the connectionidentifier that identifies the physical attachment point of access node620 that broadcasted signal 640. Said message 650 is thus destined foraccess node 620 although it is sent to access node 610. Note that sinceend node 630, in the FIG. 6 example, does not have an uplink with accessnode 620 it can not send message 650 directly to said access node 620.

Access node 610 receives message 650 and examines the CID field,corresponding to CID 520 of FIG. 5, of message 650 and realizes, fromthe stored CID to link layer identification information that it does notidentify one of its own physical attachment points. In such a case,access node 610 searches its memory for said CID of message 650 to finda mapping to a corresponding higher layer identifier for access node 620(e.g., an IP address).

For example, a base station which includes multiple sectors operatingunder a single link layer controller and/or multiple carriers used undera single link layer controller may have multiple CIDs corresponding to alink layer identifier corresponding to a single link layer controller.In embodiments where separate link layer controllers are used for eachsector and/or carrier, different link layer identifiers may be used foreach for the different sector and/or carriers. In some embodiments,there is a one to one mapping between physical attachment points andlink layers but this is not necessary and there may be several physicalattachment points operating under a single link layer. Thus, multiplephysical layer identifiers may correspond to the same link layer linkidentifier but each physical layer identifier connection identifiernormally maps to, at most, a single link layer link identifier.

Assuming a mapping to a higher layer address is found, access node 610encapsulates at least part of message 650 into a network layer message660 which includes a destination address set to the identifier of accessnode 620 and transmits said message 660 to access node 620. According tothis invention message 660 also includes an end node 630 identifier,said identifier being, depending on the embodiment, one of an end node630 IP address, end node 630 Network Access Identifier (NAI) and atemporary identifier. Access node 620 receives said message 660 andextracts the encapsulated part of message 650 from it. Access node 620inspects the CID field of the extracted encapsulated part of message 650and recognizes that the CID field identifies one of its own physicalattachments points.

Access node 620 sends message 670 which includes at least part ofmessage 650 received encapsulated in message 660 by access node 620.Said message 670 also includes an end node 630 identifier similar to theone included in message 660. Access node 610 then receives message 670and by examining the end node identifier included determines that themessage 670 encapsulates a message 680 destined to end node 630. Accessnode 610 then sends message 680 which includes at least part of themessage 670. According to this invention message 680 includes the CID ofthe physical attachment point of access node 620 that broadcasts signal640.

End node 630 receives message 680 from access node 610 but by examiningthe CID field included in said message 680, e.g., by comparing it tostored CID information, it determines that message 680 is originatedfrom access node 620 in response to message 650 sent to it earlier.

FIG. 7 illustrates exemplary signaling performed in accordance withvarious embodiments of the invention. The signaling is illustrated inthe context of exemplary system 100 illustrated in FIG. 1. End node 710is a simplified depiction of end node 200 of FIG. 2 and it is the sameas, or similar to, to the end nodes 144, 146, 144′, 146′, 144″, 146″ ofsystem 100 in FIG. 1. Access Nodes 740 and 750 are similar to accessnodes 140, 140′ and 140″ of system 100 in FIG. 1 and they areimplemented using access node 300 of FIG. 3. In FIG. 7, end node 710includes a message generation module 720 and a link selection module730. The message generation module 720 of FIG. 7, can be used byapplications running in end node 710 to generate messages for theirpurposes. For example a connection control protocol application maybeincluded and active in end node 710 allowing the end node 710 tocommunicate with access nodes for the purpose of creating, disconnectingand/or modifying links between end node 710 and one or both of accessnodes 740, 750. Another example is a quality of service (QoS)application which may be included in end node 710. The QOS applicationwhen present can modify QoS characteristics of the various links of endnode 710. Link selection module 730 of FIG. 7 measures various metricsfor the quality of connections including link latency, link channelconditions, link error rate, and link transmission power requirements todetermine, e.g., on a message by message basis or at a particular pointin time, which of the available links is the most appropriate for thetransmission of the next message.

The resulting link quality information can, and in various embodimentsis, used to determine which of the plurality of simultaneous links towhich a message should be transmitted at a particular point in time.

In FIG. 7, end node 710 maintains bidirectional links with access nodes740 and 750, which means that it can send messages to and receivedmessage from access node 740 and 750. In this embodiment of theinvention the message generation module 720 of end node 710 generatesmessage 759 with ultimate destination access node 740. Message 759 isfirst sent in link selection module 730 of end node 710. Link selectionmodule 730 selects the link between the links to access nodes 740 and750 over which the next message is to be transmitted. The linkdetermination function is based on link characteristics including atleast one of link latency, link channel conditions, link error rate, andlink transmission power requirements.

In the exemplary embodiment of this invention depicted in FIG. 7, thelink selection module 730 selects the link to access node 740 andtransmits message 760 over it. Message 760 includes at least some partof message 759 and, in some embodiment of the invention, includesadditional fields used for the transmission of a message over the linkbetween end node 710 and access node 740. For example, the additionalfields are, in some embodiments, link framing fields. Since the ultimatedestination of message 759 and 760 is access node 740, access node 740receives message 760, processes the received message and responds, e.g.,by transmitting message 765 to end node 710. Message 765 is received byend node 710 and delivered to the message generation module as message766. Message generation module 720, generates a second message 769 withthe ultimate destination being the access node 740. Message 769 is sentto link selection module 730 which selects the link over which message769 is to be transmitted. In this embodiment of the invention the linkto access node 750 is selected and message 770 is transmitted to accessnode 750. Message 770 includes at least a part of message 769 and insome embodiments of this invention includes additional fields used forthe transmission of the message over the link between end node 710 and750. For example, the additional fields are, in some embodiments linkframing fields.

In one embodiment of this invention the link selection module 730 addsan identifier, e.g., a physical attachment point identifier, of accessnode 740 together with at least a part of message 769 in comprisingmessage 770, because the link selected by link selection module 730 forthe transmission of message 770 does not correspond to the ultimatedestination of message 770, which is access node 740. In anotherembodiment of this invention the link selection module adds theidentifier of the ultimate destination of message 760 and 770 before ittransmits said messages 760 and 770, independently from which link isselected for their transmission. In a further embodiment of thisinvention messages 759, 769 include the identifier of their ultimatedestination. For example in an example of the exemplary embodiment ofFIG. 7 the identifier of the ultimate destination corresponds to accessnode 740.

In one exemplary embodiment of this invention, message 770 isimplemented according to message 500 of FIG. 5, where CID field 520identifies access node 740. Access node 750, receives message 770 andprocesses it. By examining the ultimate destination of message 770,e.g., a physical attachment point identifier in the CID field 520 ofmessage 500 of FIG. 5, access node 750 determines that message 770 isnot intended for itself but for some other node identified by theultimate destination identifier (e.g., a CID in the CID field). TheAccess node 750 looks up the physical attachment point identifier (PID)included in message 770 in its address resolution table (see addressresolution table 311 in access node 300 of FIG. 3) to find the networkaddress (e.g., IP Address) corresponding to the PID included in message770.

Access node 750 encapsulates at least a part of message 770 in anappropriate network layer header and transmits message 775 to accessnode 740. Message 775 includes at least: a part of message 770, and atleast some of the IP address of access node 740. In addition the message775 may ad in various embodiments does include some or all of thefollowing: the IP address of access node 750, the PID of access node 740included in message 770, the PID of access node 750 over which message770 was received, end node 710 identifier and session identifiers forthe encapsulation (also called tunneling) of messages between accessnode 750 and access node 740. Access Node 740 receives message 775 whichit recognizes as a message intended for itself from the destination PIDincluded in message 775.

In one embodiment of this invention access node 740 responds bytransmitting message 780 which includes at least part of message 775.Access node 750 receives message 780, which includes end node 710identifier and sends message 785 to end node 710. Message 785 includesat least part of message 780. End node 710 receives message 785 andforwards message 786 to message generation module 720.

In another embodiment of this invention access node 740 responds bytransmitting, to endnote 710, message 780′ including at least part ofmessage 775. Message 780′ is transmitted over the direct link betweenaccess node 740 and end node 710.

FIG. 8 illustrates exemplary signaling performed in accordance withexemplary embodiments of the invention where an end node is used as partof a neighbor discovery and CID routing information update process. Thesignaling is illustrated in the context of an exemplary system such asthe system 100 illustrated in FIG. 1. End node 810 is a simplifieddepiction of end node 200 of FIG. 2 and it is the same as or similar tothe end nodes 144, 146, 144′, 146′, 144″, 146″ of system 100 in FIG. 1.Access Nodes 840 and 850 are the same as or similar to access nodes 140,140′ and 140″ of system 100 in FIG. 1 and they may be implemented, e.g.,using access nodes of the type illustrated in FIG. 3. In the FIG. 8example end node 810 has a bidirectional communications link with accessnode 840, allowing it to send messages to, and receive message fromaccess node 840.

In FIG. 8, end node 810 generates and transmits message 860 to accessnode 840. Message 860 includes an identifier that identifies access node850 as the destination of said message. Access node 840 receives message860 and attempts to resolve the access node 850 identifier included insaid message to a network address, by searching its address resolutiontable, e.g., address resolution table 311 of access node 300 of FIG. 3.In the FIG. 8 example access node 840 fails to resolve said identifier.Access node 840 then transmits message 865 to end node 810. Message 865includes an indication that routing of a message was not possible due toa resolution failure.

In one embodiment of this invention end node 810 at this pointestablishes a bidirectional communications link with access node 850 byexchanging a variety of messages shown as double arrowed message 870 inFIG. 8. However, this is not necessary if a bidirectional link alreadyexists with access node 850. In another example in which the inventionis used end node 810 already has a bidirectional link with access node850 in addition to the link with access node 840

Using the link with access node 850, the end node 810 transmits a newneighbor notification message 875 to access node 850. Message 875includes at least an identifier of access node 840 and the network layeraddress of access node 840. In this way, the access node 850 is suppliedwith both an identifier, e.g., PID of access node 840 and acorresponding link layer address, e.g., MAC address which the accessnode 850 can address and store for future resolution of physical layerto network layer identifier. In one embodiment of this invention theaccess node 840 identifier is a physical attachment point identifier; inanother embodiment of this invention it is a link layer identifier. Thenetwork layer identifier of access node 840 is known to end node 810from communication messages 897 communicated to end node 810 during orafter the establishment of the link with access node 840.

In an alternative embodiment of this invention end node 810 sendsmessage 875′ instead of message 875. Message 875′ has the same orsimilar message content to message 875 but is sent to access node 850via access node 840, instead of access node 850 directly. Access node840 then routes message 875′ as message 875″ to access node 850. Notethat unlike message 860, message 875′ is a network layer messageincluding the access node 850 network address as its destination. Thenetwork address of access node 850 is known to end node 810 fromcommunication messages 899 communicated during or after theestablishment of the link with access node 850. For this reason, accessnode 840 can route message 875″ to access node 850 using a networkaddress of access node 850 e.g., IP address, without having to perform aCID to address resolution operation.

Access node 850 receives message 875 and sends new neighbor creationmessage 880 to the network address of access node 840, retrieved frommessage 875. Message 880 includes connection identifier to network layeraddress mappings for access node 850. In another embodiment of thisinvention, message 880 includes link layer identifiers to network layeraddress mappings for access node 850. In another embodiment of thisinvention message 880 includes additional neighbor information used forthe accommodation of end node handoffs, including but not limited totunnel address and tunnel session identifiers for packet redirectionbetween access nodes 840 and 850, access node 850 capabilities withrespect to quality of service, loading, protocols, and applicationssupported. Access node 840 receives message 880 and stores informationincluded in message 880 in its memory e.g., for future use in CID tonetwork address resolution operations. Access node 840 responds withmessage 882 acknowledging the reception of said information included inmessage 880.

In one embodiment of this invention access node 840 includes in message882 some of connection identifier to network layer address mappings foraccess node 850, link layer identifiers to network layer addressmappings for access node 850, neighbor information used for theaccommodation of end node handoffs, including but not limited to tunneladdress and tunnel session identifiers for packet redirection betweenaccess nodes 840 and 850, and or information indicating capabilities ofaccess node 840 with respect to quality of service, loading, protocols,and applications supported. Access node 840 receives message 880 andstores information included in message 880 in its memory, or e.g., forfuture use in routing messages. In this particular embodiment of theinvention messages 883 and 884 are not used.

In another embodiment of this invention access node 840 message 882includes an acknowledgement of the reception of the information includedin message 880. In this embodiment of the invention access node 840sends message 883 including at least some of connection identifier tonetwork layer address mappings for access node 850, link layeridentifiers to network layer address mappings for access node 850,neighbor information used for the accommodation of end node handoffs,including but not limited to tunnel address and tunnel sessionidentifiers for packet redirection between access nodes 840 and 850,access node 840 capabilities with respect to quality of service,loading, protocols, and applications supported. Access node 850 receivesmessage 883 and stores the information included in message 883 in itsmemory, e.g., for future use. Access node 850 responds with message 884acknowledging the reception of said information.

Following the exchanges of neighboring information and identifier toaddress mappings between access node 840 and 850 via message 880, 882and optionally 883 and 884, end node 810 sends message 890 to accessnode 840. Like message 860, in one embodiment of the invention message890 is also the same as or similar to message 500 of FIG. 5. Message 890identifies as its ultimate destination access node 850. Access node 840,receives message 890, searches its memory for a mapping between theaccess node 850 identifier and a network address for said node 850 andfinds said network address in its address resolution table which wasearlier populated by message 880. Access node 840 encapsulates message890 according to information in the resolution table and sends it toaccess node 850 in the form of message 891. Access node 850 respondswith message 892 again using information in its address resolution tableand message 891. Access node 840 sends message 893 to end node 810including at least part of message 892 received from access node 850completing the communication exchange between end node 810 and accessnode 850 via access node 840.

In the above described manner, through the use of messages from end node810, access nodes 840 and 850 are provided with address and/or PIDinformation about each other that can be used in routing subsequentlyreceived messages. Accordingly, as access nodes are added to thenetwork, end nodes can serve to discover their presence from broadcastsignals and notify access nodes of new neighbors. As part of thenotification process sufficient address information is distributed tofacilitate network PID based routing of messages after the notificationprocess has been completed.

In various embodiments nodes described herein are implemented using oneor more modules to perform the steps corresponding to one or moremethods of the present invention, for example, signal processing,message generation and/or transmission steps. Thus, in some embodimentsvarious features of the present invention are implemented using modules.Such modules may be implemented using software, hardware or acombination of software and hardware. Many of the above describedmethods or method steps can be implemented using machine executableinstructions, such as software, included in a machine readable mediumsuch as a memory device, e.g., RAM, floppy disk, etc. to control amachine, e.g., general purpose computer with or without additionalhardware, to implement all or portions of the above described methods,e.g., in one or more nodes. Accordingly, among other things, the presentinvention is directed to a machine-readable medium including machineexecutable instructions for causing a machine, e.g., processor andassociated hardware, to perform one or more of the steps of theabove-described method(s).

Numerous additional variations on the methods and apparatus of thepresent invention described above will be apparent to those skilled inthe art in view of the above description of the invention. Suchvariations are to be considered within the scope of the invention. Themethods and apparatus of the present invention may be, and in variousembodiments are, used with CDMA, orthogonal frequency divisionmultiplexing (OFDM), or various other types of communications techniqueswhich may be used to provide wireless communications links betweenaccess nodes and mobile nodes. In some embodiments the access nodes areimplemented as base stations which establish communications links withmobile nodes using OFDM and/or CDMA. In various embodiments the mobilenodes are implemented as notebook computers, personal data assistants(PDAs), or other portable devices including receiver/transmittercircuits and logic and/or routines, for implementing the methods of thepresent invention.

What is claimed is:
 1. A wireless terminal configured to select one ofmultiple available communications links for transmitting messages,comprising: circuitry configured to simultaneously maintain a firstcommunications link with a first access node and a second communicationslink with a second access node, determine a first physical layerattachment point identifier from multiple broadcast signals transmittedby the first access node, determine a second physical layer attachmentpoint identifier from multiple broadcast signals transmitted by thesecond access node, generate a message including the first physicallayer attachment point identifier, select only the second communicationslink to communicate the message, and transmit the message with the firstphysical layer attachment point identifier that identifies the firstaccess node to the second access node via the second communicationslink, wherein the first communications link terminates at the firstaccess node at a first physical attachment point identified by the firstphysical layer attachment point identifier, wherein the secondcommunications link terminates at the second access node at a secondphysical attachment point identified by the second physical layerattachment point identifier, and wherein selecting only the secondcommunications link occurs while the first communications link and thesecond communications link are simultaneously maintained.
 2. Thewireless terminal of claim 1, wherein selecting only the secondcommunications link is based on at least one of link latency, linkchannel conditions, link error rate, and link transmission powerrequirements.
 3. The wireless terminal of claim 1, wherein the firstphysical layer attachment point identifier comprises a cell identifier.4. The wireless terminal of claim 3, wherein the first physical layerattachment point identifier further comprises a carrier identifier. 5.The wireless terminal of claim 4, wherein the first physical layerattachment point identifier further comprises a sector identifier. 6.The wireless terminal of claim 1, wherein the first and second accessnodes are base stations, and wherein transmitting the message comprisestransmitting orthogonal frequency division multiplexing signals.
 7. Amethod for selecting one of multiple available communications links fortransmitting messages, comprising: simultaneously maintaining, by awireless terminal, a first communications link with a first access nodeand a second communications link with a second access node, wherein thefirst communications link terminates at the first access node at a firstphysical attachment point identified by a first physical layerattachment point identifier, and wherein the second communications linkterminates at the second access node at a second physical attachmentpoint identified by a second physical layer attachment point identifier;determining the first physical layer attachment point identifier frommultiple broadcast signals transmitted by the first access node;determining the second physical layer attachment point identifier frommultiple broadcast signals transmitted by the second access node;generating a message including the first physical layer attachment pointidentifier; selecting only the second communications link to communicatethe message while the first communications link and the secondcommunications link are simultaneously maintained; and transmitting themessage with the first physical layer attachment point identifier thatidentifies the first access node to the second access node via thesecond communications link.
 8. The method of claim 7, wherein selectingonly the second communications link is based on at least one of linklatency, link channel conditions, link error rate, and link transmissionpower requirements.
 9. A non-transitory machine-readable medium for awireless terminal, the machine-readable medium comprising instructionsthat are executable by a processor to: simultaneously maintain a firstcommunications link with a first access node and a second communicationslink with a second access node, wherein the first communications linkterminates at the first access node at a first physical attachment pointidentified by a first physical layer attachment point identifier, andwherein the second communications link terminates at the second accessnode at a second physical attachment point identified by a secondphysical layer attachment point identifier; determine the first physicallayer attachment point identifier from multiple broadcast signalstransmitted by the first access node; determine the second physicallayer attachment point identifier from multiple broadcast signalstransmitted by the second access node; generate a message including thefirst physical layer attachment point identifier; select only the secondcommunications link to communicate the message while the firstcommunications link and the second communications link aresimultaneously maintained; and transmit the message with the firstphysical layer attachment point identifier that identifies the firstaccess node to the second access node via the second communicationslink.
 10. The machine-readable medium of claim 9, wherein selecting onlythe second communications link is based on at least one of link latency,link channel conditions, link error rate, and link transmission powerrequirements.